1. Technical Field
The present invention relates generally to cameras and, more particularly, to deploying lens cameras having automatic focus and parallax correction capability.
2. Background Art
In a conventional autofocus camera, the viewfinder is stationary and the taking or objective lens is movable in either direction along a straight-line path (optical axis) which is generally perpendicular to the film plane. Some cameras, such as the Konica A4, have a deploying objective lens, where the lens is stored in the body of the camera and deployed straight out along the optical axis to its focus or operational positions. Deployment of the objective lens from its stored position is achieved by slidably engaging a lens housing or support (containing the lens) onto a pair of guide rods, as in the Konica A4 camera, or as disclosed in U.S. Pat. No. 2,552,244 to White.
This arrangement has a substantial drawback in that the deployment distance is limited by the length of the guide rods which is, in turn, limited by the depth requirement of the camera housing. Further, the deployment distance is limited by any bearing assembly (e.g., a bushing or sleeve pair) engaging the guide rods. An effort to maximize the deployment distance by shortening the length of the bearing assembly is limited by stability considerations of the objective lens.
In another known configuration, lens deployment is achieved by means of extendable/retractable X-shaped linkages, as disclosed in U.S. Pat. No. 4,894,672 to Tanaka an U.S. Pat. No. 4,326,783 to Kawamura et al. This configuration suffers from the inherent problems associated with a design having a large number of moving parts, including relatively low reliability and high manufacturing cost. The intricate assembly also limits efforts to minimize the depth dimension of the camera housing.
In conventional autofocus and manual focus cameras, parallax correction becomes necessary for near field focus positions. In such cameras, the optical axes of the viewfinder and that of the objective lens are parallel to each other and separated by some interaxial distance. As a result, for relatively close object focusing, the position of the object image as seen in the viewfinder will not coincide with the position of the object image that is focused onto the film by the objective lens.
In one known method, the user performs parallax correction by selecting the position of the viewfinder, relative to the object, with the aid of auxiliary lines in the viewfinder and by judging the distance of the object. For the ordinary user, this correction method is both difficult to understand and to perform.
Other known approaches to parallax correction include the adjustment of the image scene through the viewfinder by movement of viewfinder frame elements as disclosed in U.S. Pat. Nos. 4,079,399 to Hopfner, 2,719,454 to Nerwin, and 2,302,584 to Steiner, or by insertion of optical prism elements in the viewfinder as disclosed in U.S. Pat. Nos. 2,730,024 to Merrick and 2,674,932 to Tydings et al. These approaches are less than optimum for autofocus cameras because the viewfinder field of view must be adjusted to match the field of view of the taking lens. Thus, the composition of the picture must occur after the camera is focused, requiring an additional delay in the taking of a picture.
A further approach to parallax correction includes movement of the viewfinder lens along a straight path, inclined relative to the optical axis of the objective lens, as disclosed in U.S. Pat. No. 2,062,585 to Laube et al. Alternatively, the objective lens has been made to move along a straight path, inclined to the optical axis of the viewfinder, as disclosed in Japanese Pat. 2,051,134 (1990). These approaches have required the use of extended guide rods upon which the lens is made to travel. Hence, they are not suitable for compact camera designs where it is desirable to retract the objective lens from its operational positions to a compact storage position.